Deficiencies in trauma care “after hours” (18:00–07:00) have been well recognised.1 Such deficiencies may be caused by the differential availability of senior staff and resources for complex procedures, fatigue of personnel and/or increased prehospital logistical difficulties (eg, flight restrictions for helicopters at night). Resource allocation and staffing are substantially more expensive after hours, and a finding of an association between time of presentation and outcomes could be used to justify improved staffing in trauma centres outside “business” hours.

Compared with patients admitted “in hours”, patients admitted after hours following injury may be intrinsically at higher risk of death by virtue of a different casemix or increased severity of illness. Crude mortality rates have been previously reported to be significantly higher among people admitted with trauma at night, compared with during the day, but no significant association has been shown after adjusting for injury severity.2–5

In recent years, mortality after trauma has been steadily decreasing, secondary to preventive strategies and improved trauma systems.6–8 Accordingly, in advanced trauma systems, a smaller…